Reducing SF₆ emissions from electrical switchgear

Abstract

SF₆ is a greenhouse gas applied in particular in electrical switchgear for the transmission and distribution of energy. It is indispensable for this purpose because of its superior electrical properties at high voltage. The consequent handling of SF₆ and the continuous effort to reduce leakage from electrical switchgear by design and material has reduced and will further reduce emissions of SF₆. Taking the German SF₆ emission data reported annually, the authors tried to relate local emission data from several sources – not only electrical switchgear – with globally reported and measured SF₆ concentrations. The latest revision of the European F-gas regulation, EU 517/2014, imposes the requirement on users to either perform regular leak search or install leakage detection systems on switchgear in service containing more than 6 kg of SF₆. International switchgear standards pose limits on the leakage rate of equipment and prescribe routine tests before delivery. The paper presents several possibilities to reduce the SF₆ emission from switchgear by design and choice of materials. Another source for emitted gas is the manual handling of SF₆. As an example for improved SF₆ handling, a “zero” emission automatic test and filling station for hermetically sealed switchgear is evaluated.

Keywords:

• F-gas regulation
• SF₆ emission
• leakage tests
• electrical switchgear

Acknowledgements

The authors are members of the “SF₆ Task Force” of the European Association of the Electricity Transmission and Distribution Equipment and Services Industry, T&D Europe.

Notes

1. Fluoronitrile and Fluorocetone mixtures with CO₂ or air are currently being investigated, with promising results for certain switchgear applications considering ambient temperature and filling pressure.

2. The Earth's radius, R_E, is 6365 km; the mean thickness of the atmosphere, D_atm, is 8.16 km; the Loschmidt constant, L, is 2.687 × 10²⁵ m^–3; and the mass, M_SF6, of an SF₆ molecule is 2.45 × 10^–25 kg.